1. Field of the Invention
The present invention relates to a wireless communication apparatus, a method of controlling the wireless communication apparatus and a storage medium storing the related program.
2. Description of the Related Art
There are wireless transmission lines that serve for the transfer of data, and the wireless LAN standard IEEE 802.11 is applicable to ordinary wireless transmission lines. In the field of wireless communications such as wireless LAN communication, there is growing demand for data transfer requiring large-capacity and real-time transfer for data such as voice data and video data which is distributed by streaming. In order to satisfy this demand, systems incorporating QoS (Quality of Service) technology have been studied in the wireless LAN standard IEEE 802.11e and proposed. In order for a wireless terminal to perform wireless communication with another device in the infrastructure mode in a wireless communication system, a wireless connection to an access point is necessary. If it is desired to perform wireless communication that requires a large-capacity, real-time transmission in such case, then it is necessary to select the access point appropriately in accordance with the communication quality requested.
For instance, in Japanese Patent Document 1 (Japanese Patent Laid-Open No. 2007-110373), which is one example of a technique for selecting an access point, a wireless terminal measures the signal strength of wireless data, which it has received from an access point, before the access-point connection is established. Further, the wireless terminal measures interfering radio waves that affect the channel used by the access point. According to the technique described, communication efficiency for a case where wireless communication with an access point would be performed is predicted based upon the results of these two measurements and the connection is established upon selecting the access point for which the highest communication efficiency would be achieved.
In another example, according to Japanese Patent Document 2 (Japanese Patent Laid-Open No. 2008-42922), first a wireless terminal performs a channel scan, receives channel information transmitted from an access point and extracts the channel utilization rate. Next, on the basis of the channel information, the wireless terminal determines the maximum data transmission rate capable of being supported by the channel. The wireless terminal statistically processes channel occupancy probability within the scanning time interval and then calculates a hidden-terminal impact factor based upon the channel utilization rate, maximum data transmission rate and channel occupancy probability. The wireless terminal selects an access point based upon the wireless-terminal impact factor.
The technology described in Patent Document 3 (Japanese Patent Laid-Open No. 2007-165980) also is available as configurations for registering and deleting connections. According to this technique, the amount of accumulation of a transmission queue for every connection ID is monitored, QoS information is ascertained based upon such monitoring and a connection is registered or deleted accordingly.